Cobalt(II)-dianthracene Frameworks: Assembly, Exfoliation and Properties.

Metal-organic frameworks containing responsive organic linkers are attractive for potential applications in sensors and molecular devices. Herein we report three cobalt(II) phosphonates incorporating responsive dianthracene linkers, namely, Co (amp H ) (H O)  ⋅ 6H O (MDAF-1), Co (amp )(H O)  ⋅ 2H O (MDAF-2) and Co(amp H ) ⋅ 2H O ⋅ 0.5DMF (MDAF-3), where amp H is pre-photodimerized 9-anthrylmethylphosphonic acid. MDAF-1 shows a layer structure in which dinuclear Co (PO H) units are inter-connected by dianthracene ligands. In MDAF-2 and MDAF-3, inorganic chains of corner-sharing {CoO } (or {CoO }) and {PO C} are cross-linked by dianthracene ligands into 3D frameworks. All compounds underwent thermo-induced phase transitions, first the de-solvation and then the de-dimerization of dianthracene (as well as the release of the remaining solvent molecules for MDAF-2 and -3), associated with magnetic changes. MDAF-1 can be exfoliated into single-layer nanosheets in water which show light-triggered luminescent changes.